A 50-year-old lady with a background of Perthes disease and multiple bilateral hip revisions presented with symptoms of right hip pain. She was unable to raise and weight bear on the right leg. Hip examination revealed limited flexion and extension to 15–20 ° due to pain. Her blood tests and x-rays showed no obvious acute problems. She was treated with mobilisation and analgesia, and had a bone scan that revealed no acute issues. Further examination revealed she had generalised weakness in her upper arm. A creatine kinase marker showed a level of over 2000. Therefore, an MRI and a muscle biopsy were done. A diagnosis of sarcoid myositis was made and the patient was put on steroids. She was able to make a full recovery. This case highlights the consideration of rare diseases in more highly complex cases.